Thermostatically controlled electric seat heaters for vehicles

ABSTRACT

A vehicle seat heater includes a main body adapted to be mounted on at least one of a seat cushion part or seat back part of a vehicle seat and provided with a pair of electric warming heaters. A thermally insulated temperature control unit located remotely from the heater main body is provided for stopping energization of the heating elements when the temperature of the seat heater main body exceeds a predetermined level. The control unit includes a pair of auxiliary electric heaters each respectively coupled to a different one of the warming heaters for simultaneous energization therewith and a pair of thermostatic switches coupled in series, with each thermostatic switch being in heat exchange relationship with a different one of the auxiliary heaters for stopping the flow of electricity to the auxiliary heater and warming heater coupled thereto. The thermostat switches and auxiliary heaters are disposed within casing or housing and connected to the respective warming heaters by lead wires.

TECHNICAL FIELD

This invention relates to a vehicle seat heater which is to be mountedon a seat cushion part and/or a seat back part of a vehicle seat.

BACKGROUND ART

In the conventional vehicle seat heater as shown in FIG. 1 and FIG. 2,seat heater main body 4 is constructed by wiring cord-shaped warmingheater 2 in zig zag shape on substrate body 1 consisting of a polyesternon-woven fabric, or the like, and by heat-press-bonding (or a similarprocess) surface cloth 3, which has a thermal fusing adhesive, on bothsides of the substrate body 1. On one part of the seat heater main body4, a thermostat 5 is mounted to directly sense the heat of the seatheater warming part 4'. Lead wires 6 are connected to the thermostat 5and the above-mentioned warming heater 2, and connection plug 7 forconnecting the vehicle seat heater to a power source (not shown) of anautomobile. The above-mentioned seat heater main body 4 is, as shown inFIG. 3, mounted on a seat part 8a and a seat back part 8b of a vehicleseat 8. The above-mentioned mounting of the seat heater main body ismade, as shown in FIG. 4, by inserting and disposing heater main body 4between a pad 9 formed of foamed urethane and a cushion material 10 madeof foamed urethane. Incidentally, numeral 11 is the surface leather ofthe vehicle seat.

In the above-mentioned configuration, however, since thermostat 5, whichcontrols the flow of electricity to the heater 2 by detecting thetemperature of the warming heater 2, is mounted on one part of the seatheater main body 4, and the seat heater main body 4 is mounted in thevehicle seat 8, the thermostat 5 causes a bump to be formed in the seatsurface, and as a result, the user feels uncomfortable when sitting onthe vehicle seat.

A solution has been proposed which mounts the thermostat in a part ofthe seat not touching the user, namely at the part where the seatcushion part 8a and the seat back part 8b are superposed, or mounting itbetween the legs of the user. However, these solutions requirethermostat temperature settings unique to each vehicle seat shape, sinceheating characteristics vary depending on respective vehicle seatconfigurations due to the shape of the vehicle seat 8 and the shape andvolume of the cushion material 10. Therefore, mounting the thermostat insuch locations has been troublesome.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the present invention providesa vehicle seat heater which has no uncomfortable feeling when the useris seated on the seat, and is capable of stably controlling the warmingheater independent of the shape and construction of the vehicle seat. Inorder to achieve this purpose, the present invention covers the controlpart, the auxiliary heater and the thermostat with heat insulationmaterial, and also disposes the control part separate from the seatheater main body and at a location other than the seat cushion part andseat back part of the vehicle seat. By this configuration, there is nouncomfortable feeling when the user is seated on the vehicle seat. Sincethe control part is not positioned in the vehicle seat, there is no needto temperature set the control part to take into account variations inthe shapes of vehicle seats.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the conventional seat heater forvehicle,

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1,

FIG. 3 is a perspective view of the vehicle seat provided with the seatheater of FIG. 1,

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 3,

FIG. 5 is an exploded perspective view of a vehicle seat heater showingone embodiment of the present invention,

FIG. 6 is a perspective view of a control part in the seat heater ofFIG. 5,

FIG. 7 is a cross-sectional view of the control part of FIG. 6 takenalong line 7--7 of FIG. 6.,

FIG. 8 is a circuit diagram of the seat heater of FIG. 5,

FIG. 9 is a temperature vs. time characteristic chart of the seat heaterof FIG. 5,

FIG. 10 is an exploded perspective view of the seat heater showinganother embodiment of the present invention,

FIG. 11a and FIG. 11b are, respectively, a side view of the controldevice and a cross-sectional view of FIG. 10 taken along line 11b--11bof FIG. 10, and

FIG. 12 is an exploded perspective view of the control device of FIG.10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

On embodiment of this invention will now be described in connection withFIG. 5 through FIG. 8. Incidentally, in FIG. 5 through FIG. 8, the samenumbers as those shown in FIG. 1 through FIG. 4 are used for likecomponents. That is, in this emboidment, lead wires 6 (which areconnected to warming heater 2) are led out from a pair of seat heatermain bodies 4 (which are mounted on the seat cushion part 8a and seatback part 8b of the vehicle seat 8), and connection plugs 7 are providedat end parts of the lead wire 6, and a control part 12 (to which theconnection plugs 7 are detachably mounted and which controls the supplyof electricity to the heater depending upon the temperature of thewarming heater 2) is provided. The control part 12, as shown in FIG. 6and FIG. 7, includes thermostats 14 having temperature sensing parts 13,auxiliary heaters 17 disposed at adjacent positions to the thermostats14 and constituted by winding heater material around a holding body 16,and a case 20 wherein auxiliary heaters 17 and the above-mentionedthermostats 14 are mounted. Auxiliary heaters 17 and thermostats 14 aremounted on a holding sheet 18 formed by a printed circuit substrate.Plug reception parts 19 are provided in which the connection plug 7 atthe end parts of lead wires 6 are detachably mounted. Terminal pins 85are provided within reception parts 19 to make electrical contact withterminal sockets on plugs 7 (not shown). A case lid 21 is provided forclosing a bottom opening of the case 20 and comprises protrusion parts21a which abut the thermostats 14. The case 20 and the case lid 21 areof heat insulation material, and the temperature sensing part 13,thermostats 14, and auxiliary heater 17 are covered by case 20 and lid21. Also, the above-mentioned thermostats 14 are mounted in the case 20in such a manner that the temperature sensing parts 13 abut the insideface of the case 20, and the auxiliary heaters 17 are disposed to heatparts of case 20 located opposite the temperature sensing parts 13 ofthe thermostats 14.

FIG. 8 shows a circuit diagram, wherein two thermostats 14 are connectedin series, and the auxiliary heaters 17 are disposed adjacent torespective ones of thermostats 14 to constitute thermostat-auxiliaryheater units 22 and 23. Furthermore, the above-mentioned auxiliaryheaters 17 and a pair of warming heaters 2 are connected in seriesrespectively by connecting members. Incidentally, the each seriesconnected pair of warming heaters 2 and the auxiliary heaters 17 arerespectively connected in parallel.

Seat cushion part sheet heater 24 is mounted to the seat cushion 8a ofthe vehicle seat 8 and is connected to one thermally connectedthermostat-auxiliary heater unit 22. Seat back part sheet heater 25 ismounted at the seat back part 8b of the vehicle seat 8 and is connectedto the other thermostat-auxiliary heater unit 23. Thus, even if onesheet heater is broken, the other thermostat-auxiliary heater unitoperates normally. Furthermore, since the two thermostats 14 areconnected in series, the current flows through the two thermostaticstages, and accordingly a double safety circuit is realized.

In this embodiment, control part 12 which is constituted by thermostats14 or the like, which stop the flow of electricity to the warming heater2 when the temperature of the heater 2 reaches a preset temperature, iscovered by heat insulation material as above-mentioned. Control part 12is also disposed separate from the pair of sheet heaters 24 and 25 ofmain body 4 which are mounted on the seat cushion part 8a and seat backpart 8b of the vehicle seat 8. Control part 12, may be placed in a spacebelow pad 9 of FIG. 4. As a result, there is no protrusion in the seatand thus no uncomfortable feeling when the user is seated on the vehicleseat 8, unlike the prior art where the thermostats are disposed on thevehicle seat. Furthermore, the above-mentioned control part 12 is notaffected by the influence of the shape and constitution of the vehicleseat 12, nor the thermal influence by heat capacity of the pad 9 shownin FIG. 4. Therefore, a thermo-timer which switches on-off at timeinterval t, as shown by β of FIG. 9, may be obtained. That is, T of FIG.9 shows the preset desired temperature, and α shows a characteristicheating curve where the time from the beginning of the rise oftemperature to achieving the present temperature is short. Curve α isnot desirable since heating is too rapid. Curve γ of FIG. 9 shows acharacteristic curve of the thermostat in which temperature rises moreslowly so that to reach the preset temperature T requires a great dealof time. Therefore, the time-temperature presetting as shown in β ofFIG. 9 is needed. In the present invention, as a result of theabove-mentioned configuration, the characteristic curve as shown by β ofFIG. 9 is obtainable. According to actual experiments, results have beenobtained in which energizing the heating elements for 30 minutes to 1hour in case the temperature outside the vehicle is -20° C., provides asufficient warmth to the seat. In such a case, even though the vehicleseat is warmed at this rate, the temperature does not reach a dangeroustemperature. It is preferable that the case wattage density of the seatheater main body 4 should be 220-226 W/m2.

Next, another embodiment of this invention is described with thereference to FIG. 10. A connection plug 27 is provided on end parts oflead wires 26 which are led out from the control part 12A, and plug 27is detachably connected to the connection plug 7 which led out fromsheet heater main body 4. Also, lead wires 26 from control part 12A areconnected to vehicle power through connection plug 28, vehicle plug 29and vehicle power lines 35. As shown in FIGS. 11a, 11b and 12, controlpart 12A is made by first making auxiliary heater 17A (used forthermostat heating) by heat pressing heaters 15 to holding body 16 whichis made of non-woven fabric or the like, and to non-flammable fabric 32.Holding bases 31 are provided having holes 30 for inserting thethermostat 14. Next, thermostats 14 (having temperature sensing parts13) are inserted in the holes 30 of the holding bases 31 so that sensingparts 13 face the auxiliary heater 17A for thermostat heating, therebyone face of the holes 30 are closed. Also, the heaters 15 and thethermostats 14 are connected by lead wires 36 and 37.

Next, the assembly of control part 12A is completed by placing acovering member 39 having square holes 38 for inserting the holdingbases 31, over the auxiliary heater-thermostat assembly and coveringmembers 34, and 40 are abutted from upper and lower sides. Syntheticresin cases 43 and 44 having flange planes 41 and 42, are fitted overthe entire assembly. The flange planes 41 and 42 thus fitted are joinedand all peripheries are welded by high frequency welding or a likeprocess.

At this time, lead wires 26 are led out of the casing. Also, a tube 33for protecting the lead wires 26 is connected to the lead wires 26.Thus, in this embodiment also, the temperature sensing part 13,thermostats 14 and auxiliary heater 17 are covered by heat insulationmaterial such as the above-mentioned covering members 34, 39, 40 and isdisposed beneath pad 9 of the vehicle seat. Also, the electric circuitof this control part 12A is as shown in FIG. 8. Also, in the controlpart 12A, the temperature rise characteristic curve of the thermostat 14is determined by the heat capacity and heat keeping capability of thethermostats 14 and environment surrounding the thermostats and not thevehicle seat. Of course, however, the characteristic curve should beconsidered to be dependent on the ambient temperature. In order toobtain sufficient warming characteristics, the heat retention capacityof control part 12A should be increased by means of the holding bases 31having a high heat retention capacity, thereby raising the temperatureslowly by appropriate control of the auxiliary heater 17A, and byretaining heat by appropriate choice of covering members 34, 39 and 40.With only the heat retention capacity of the thermostats 14, the heatingcharacteristic curve becomes like α of FIG. 9, and unless heat retentioncapacity of the heater is carefully chosen, the characteristic curvewill become like α or γ. Furthermore, unless an appropriate choice ofcovering members 34, 39 and 40 is made, the characteristic curve becomeslike γ. Also, the heat retention capacity of control part 12A can bedetermined by a product of weight and specific heat. According toexperiments, the weight of the thermostats 14 and the weight of theholding bases are, in total, preferably 20-25 g, and the auxiliaryheater 17A is preferably supplied with about 1 W-2 W, and the thicknessof urethane foam covering members 34, 39 and 40 is preferably 8-15 mmeach when piled in three layers. Thereby, appropriate characteristiccurve β of FIG. 9 has been obtained.

The embodiments described in FIG. 5 through FIG. 12 have the followingeffects:

(a) Since two thermostatic stages are connected in series, current flowsthrough two stages of the thermostats 14, thereby a double safetycircuit can be obtained;

(b) Since each warming heater 2 is connected in series with a thermostat14 and an auxiliary heater 17, and the two thermostat-warming heaterassemblies are connected in parallel, even if one of the warming heaters2 is cut off and one thermostat 14 does not operate, the otherthermostat operates normally and a state of extraordinary overheating orburning out of an element or a like danger does not take place;

(c) Since the control part 12 or 12A is separated from the warmingheater 2 and the thermostats 14 are not provided in the seat as theprior art, there is no uncomfortable feeling when the user is seated;

(d) Maintenance is simplified since the control part 12A can be easilyreplaced by disconnecting/connecting the connection plugs 7, 27 and 28;and

(e) Since temperature setting of the thermostats 14 is now unnecessary,even if a cushion, thick seat cover, cloths or the like are left on theseat during the ON state of the warming heater 2, extraordinaryoverheating or burning or the like can be prevented.

As above-mentioned, according to the present invention, there is nouncomfortable feeling when the user is seated on the vehicle seat, sincecontrolling parts such as the thermostats are not disposed on thevehicle seat as in the prior art. Also, even if there are variations inthe shape or configuration of the vehicle seat, there is no need toindividually set the temperature of the control part such as athermostat to correspond to the seat configuration, as required in theprior art. Furthermore, even if a cushion, thick seat cover, cloths orthe like are left on the vehicle seat at the ON state of the warmingheater, an overheating condition will be prevented since the controlparts such as the above-mentioned thermostats are configured to stopsupplying electricity to the heater when the temperature of the warmingheater exceeds the present temperature. Thus, the present inventionprovides a vehicle seat heater which operates in a stable state and hasincreased safety.

Furthermore, since the heat retention capacity and temperature keepingstate of the thermostats and elements surrounding the thermostats canalways be kept constant, there is no thermal influence on thethermostats by the shape, size and configuration of the seat cushionpart and the seat back part of the seat, and a seat heater having aconstant characteristic curve is obtainable, thus making operation ofthe vehicle seat heater highly reliable and safe.

I claim:
 1. A vehicle seat heater comprising:a seat heater main bodyadapted to be mounted on at least one of a seat cushion part and a seatback part of a vehicle seat, said seat heater main body including a pairof electric warming heaters; temperature control means for stopping theflow of electricity to said electric warming heaters when thetemperature of said seat heater main body exceeds a predetermined level,said control means being covered by a heat insulation material andadapted to be disposed at location separate from said seat heater mainbody, said control means including: a pair of auxiliary heaters eachrespectively coupled to a different one of said pair of electric warmingheaters and adapted to be energized and deenergized simultaneously withthe associated electric warming heater, said auxiliary heaters beingcovered by said heat insulation material; and a pair of thermostaticswitches coupled in series, each thermostatic switch being in heatexchange relationship with a different one of said auxiliary heaters,for stopping said flow of electricity to said warming heater and saidauxiliary heaters; said thermostatic switches being covered by said heatinsulation material; and coupling means for coupling said thermostaticswitches to said electric warming heaters.
 2. A vehicle seat heateraccording to claim 1 wherein said coupling means includes lead wireseach having a first end with at least one connection plug for connectionto said control means, and wherein each said thermostatic switchincludes a sensing member for sensing temperature, and wherein saidcontrol means includes:a casing for holding said thermostatic switchesand said auxiliary heaters so that each said sensing member abuts a wallof said casing and said auxiliary heaters are disposed internal to saidcasing to cause said casing to be heated simultaneously with saidelectric warming heaters; and at least one receptacle centrally disposedin said casing for receiving said connection plug.
 3. A vehicle seatheater according to claim 1 wherein each said thermostatic switchincludes a sensing member for sensing temperature, and wherein saidcoupling means includes lead wires each having a first end coupled inseries with a respective on of said thermostatic switches and theassociated auxiliary heater, and wherein said control meansincludes:said heat insulation comprising at least one heat insulatingmember surrounding said thermostatic switches and said auxiliaryheaters, and said at least one insulating member holding saidthermostatic switches and said auxiliary heaters in such a manner as tocause each said sensing member to closely abut an associated one of saidauxiliary heater; and a housing for holding said at least one heatinsulating member and said thermostatic switches and said auxiliaryheaters in assembled relationship.